The invention relates to a method and apparatus for use with submersible electrical equipment.
Electrical equipment, such as an electric motor (a DC motor, for example), may be used in an environment that would otherwise cause the equipment to fail if not for protective measures that are in place to shield the equipment from the environment. For example, referring to FIG. 1, a motor 14 may be part of a valve 10 that controls the flow of well fluid from a producing formation into a production tubing 12. In the operation of the valve 10, the motor 14 actuate a ball screw drive 20 to move a generally cylindrical sleeve 26 (that closely circumscribes the outside of the tubing 12) to either open or close radial ports 8 of the tubing 12 to the flow of well fluid. The valve 10 may be located in an annulus of the well that is filled with well fluid, and unfortunately, the motor 14 may be damaged and may fail if the well fluid contacts the motor 14, as the well fluid may be electrically conductive.
For purposes of isolating the motor 14 from the well fluid, the motor 14 may be located in a chamber 15 of a sealed housing 11 of the valve 10. To further protect the motor 14, the chamber 15 may be filled with a nonconductive, or dielectric, oil.
A potential difficulty with the above-described arrangement is that the seals of the housing 11 may eventually leak and allow the well fluid to gradually flow into the chamber 15 and displace the oil. An operator at the surface of the well may be unaware of this contamination, and as a result, the motor 14 (and thus, the valve 10) may fail without warning. As a result, the operator may unexpectedly loose control of the valve 10 and not be able to plan and take remedial actions (final positioning of the valve, as an example) in anticipation of complete valve failure. Thus, production may be lost due to the unexpected loss of valve control.
Thus, there is a continuing need for a system to monitor and/or predict failure of submersible electrical equipment.